Heat resistant alloys



PatentedJan. 11, 1938 UNlTEDiSTATES PATENT OFFICE Willi Giidecire,Witteu-R ler, Berlin-Dahlem,

aim and William Gu'ert- Germany to llsnors Degea Aktiengesellschalt(Auergesellschaftb- Berlin, Germany, a corporationo! Germany No No94,286.

Application Aus'ust 4, 1936, Serial In Germany August 9, 1935 2' Claims.(c1. 75-424) It is known that iron-chromium-aluminium alloys, forexample alloys in which the main constituent is iron and which alsocontain about 20-35% of chromium and about 1-10% 01 aluminium, are veryresistant to high temperatures,- i. e. to the efiect of the oxygen 01'the air at high temperatures.

It has now been found that the resistance to heat oi such alloys can beconsiderably further increased by adding a proportion of metallicthorium to them. The advantageous eiiect of the thorium is alreadyapparent with the addition of very small amounts, for example an amountof 0.001% or less.

The amounts employed in practice will: generally be between 0.001and,5%. In some cases, however, a higher proportion 01' thorium may beadded. The amount of thorium to be added depends on the degree ofincrease of resistance, to the effect of oxygen at high temperatureswhich is to be obtained, on the mechanical properties desired in thealloy and flnallyon considerations of economy.

For the p se of varying the mechanical properties of the alloys, forexample their capability of being worked, small proportions 01' othermetals, for example manganese, silicon,. magnesium and the like may alsobe incorporated. The amount of such additional metals which is added maybe for example from 0.01 to 2%.

The alloys manufactured in accordance with the invention represent aparticularly valuable material i'or making articles which have to resistmium. and 5% aluminium became Comparative experiments-have proved thatthe life at a temperature or 1250" C. of resistance wires, forelectrically heated appliances-and the like, made of an alloy 01' 65%iron, chrolong with the addition of 0.05% thorium, 3% times with theaddition or 0.1% thorium and 7 times with the addition of 0.5% thorium.The iron-.chromium-aluminium alloys manufactured in accordance with theinvention with 10v the addition of thorium have the further greatadvantage that the variation in their resistance is less. Thus, forexample, the resistance of an electric resistance wire made of aniron-chromium-aluminium alloy of the aforesaid composition when heatedto 1250 C. increased in its life or about eisht hours by as comparedwith its resistance at'the start. The increase in resistance of an alloy01' a similar composition but with a content of 1% of thorium on theother 20 hand was only 27% ai'ter being heatedi'for 56 hours at s.temperature of 1250" C. a

- We claim? 1. A heat resistant alloy which consists of 7 '.-about 1-10%or aluminum, about 20-35% of chromium, about .001-5% of thorium and theremainder substantially of iron.

3 2. Anelectrlc resistance clement an alloy consisting oi about 1-10% ofabout 20-35% of chromium, about comprising thorium and the remaindersubstantially 01 iron.

wnn 66 m.

wnmuouna'ima. f

aluminum,

